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Search Results: 1 - 10 of 139811 matches for " Elena V. Todorova "
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Structure and Properties of Functionalized Porous Silica Hybrid Materials  [PDF]
Elena V. Todorova, Georgi E. Chernev, Stoqn P. Djambazov
Open Journal of Inorganic Non-metallic Materials (OJINM) , 2014, DOI: 10.4236/ojinm.2014.43006
Functionalized silica hybrid materials are extensively studied and applied materials in the field of science and technology. Functionalization is an approach, which allows for the application of organic components in the improvement of the design, properties and potential application of silicate materials. Silica hybrid materials, functionalized via incorporation of organic components (chitosan and methacrylic acid) were synthesized by the sol-gel method. The base silica structure of the hybrids was obtained via hydrolysis and condensation of the silicate precursor, tetraethyl orthosilicate. The investigations of synthesized hybrids are focused on the influence of the nature and quantity of functional organic components on their final structures and properties. The structural characteristics of obtained hybrid materials were investigated using XRD, FTIR, SEM and DTA/TG analysis. The obtained results presented the formation of amorphous porous structure and the organic components are evenly distributed into the silica network. The functional radicals of chitosan and methacrylic acid (amine, hydroxyl groups) exist in the hybrid structure as free reactive centers, as their quantity increases with increasing the organic amount. The swelling behavior in acidic and neutral solutions of the synthesized materials is investigated and the results presented, that the silicate materials exhibit hydrophilic character.
World Demand as a Determinant of Immiserizing Growth  [PDF]
Tamara Todorova
iBusiness (IB) , 2010, DOI: 10.4236/ib.2010.23033
Abstract: Theoretically economic growth could have negative effects over the growing economy when production expands for products the world demand for which is inelastic. If growth occurs in sectors and for products the world demand for which is elastic it could be expected that total revenues to domestic producers and exporters increase. Our goal is to prove that growth would be immiserizing only for products for which world demand is inelastic and expansion leads to a sizable worsening of the terms of trade. We show that there are few such commodities, namely food products and natural resources such as oil. Studying econometrically the demand function for Brazilian coffee as an example, we compare our estimation of the elasticity of demand for Brazil’s exports of green coffee with other research on the world elasticity of demand for green coffee. We conclude that for manufactured products the demand for which is highly elastic it is unlikely that exporting countries fall into immiserization, therefore, growth and further participation in global trade turn out to be quite beneficial. Our conclusion is that too much emphasis is put in economic theory and trade policy on the concept of immiserizing growth which is more of a theoretical possibility than a real-life problem.
Cloning, purification and characterization of the ribosomal protein L11 from E. coli  [PDF]
Roumiana Todorova
American Journal of Molecular Biology (AJMB) , 2011, DOI: 10.4236/ajmb.2011.11005
Abstract: A high-expression system of L11 was constructed and investigated its interaction with other elements of the ribosome using physicochemical methods. The gene rplK, coding for the protein L11 from the E. coli 50S ribosomal subunit was amplifyied, cloned and over-expressed. The protein L11 was purified under native and denaturing conditions, refolded and the structure of both proteins was compared. The protein L11 properly refolded from 6M urea after dialysis. Experiments on binding of proteins L11, RRF and EF-G from Escherichia coli were performed by ana-lytical centrifugation and Biacore. Specific binding between protein L11 and RRF by analytical cen-trifugation was not detected probably due to struc-tural reasons. These findings may be helpful in the design of new antibiotics that specifically disrupt the interactions in the “GTP-associated site” of the bac-terial ribosome, as many of them are not effective anymore. A common intrinsically disordered region of protein L11 was found to be the amino acid se-quence 86-97, while the residues 67-74, containing the linker region, are predicted to be disordered by DisEMBL.
Disorder structural predictions of the native EWS and its oncogenic fusion proteins in rapport with the function  [PDF]
Roumiana Todorova
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.31005
Abstract: The Intrinsic structural disorder (ISD) of native EWS and its fusion oncogenic proteins, including EWS/FliI, EWS/ATF1 and EWS/ZSG, was estimated by different Predictors. The ISD difference between the wild type and the oncogenic fusions found in the CTD is due to the fusion partner, usually a transcription factor (TF). A disordered region was found in the sequence (AA 132 - 156) of the NTD (EAD) of EWS, consisting of the longest region free of Y motifs. The IQ domain (AA 258 - 280), a Y-free region, flanked by two Y-boxes, is also disordered by all used Predictors. The EWS functional regions RGG1, RGG2 and RGG3 are predominantly disordered. A strong dependence was found between the structure of EWS protein and its oncogenic fusions, and their estimated ISD. The oncogenic function of the fusions is related to a decreased ISD in the CTD, due to the fused TF. The Predictors shown that the different isoforms have similar profiles, shifted with some amino acids, due to the translocations. On the bases of the prediction results, an analysis was made of the EWS sequence and its functional regions with increased ISD to make a relationship sequence-disorder-function that could be helpful in the design of antitumor agents against the corresponding malignances.
The Economic Dynamics of Inflation and Unemployment  [PDF]
Tamara Todorova
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.22025
Abstract: We study the time path of inflation and unemployment using the Blanchard treatment of the relationship between the two and taking the monetary policy condition into account. We solve the model both in continuous and discrete time and compare the results. The economic dynamics of inflation and unemployment shows that they fluctuate around their intertemporal equilibria, inflation around the growth rate of nominal money supply, respectively, and unemployment around the natural rate of unemployment. However, while the continuous-time case shows uniform and smooth fluctuation for both economic variables, in discrete time their time path is explosive and nonoscillatory. The hysteresis case shows dynamic stability and convergence for inflation and unemployment to their intertemporal equilibria both in discrete and continuous time. When inflation affects unemployment adversely the time paths of the two, both in discrete and continuous time, are dynamically unstable.
Gradient dynamics description for films of mixtures and suspensions - the case of dewetting triggered by coupled film height and concentration fluctuations
Uwe Thiele,Desislava V. Todorova,Hender Lopez
Physics , 2013, DOI: 10.1103/PhysRevLett.111.117801
Abstract: A gradient dynamics model based on an extended interface Hamiltonian is presented that is able to describe the dynamics of structuring processes in thin films of liquid mixtures, solutions and suspensions on solid substrates including coupled dewetting and decomposition. After discussing known limiting cases the model is employed to investigate the dewetting of thin films of liquid mixtures and suspensions under the influence of effective long-range van der Waals forces that depend on solute concentration. The occurring fluxes are discussed and it is shown that spinodal dewetting may be triggered through the coupling of film height and concentration fluctuations. Fully nonlinear calculations provide the time evolution and resulting steady film height and concentration profiles.
Representation of “I-Stranger” Interaction as a Communication Risks Predictor  [PDF]
Elena V. Ryaguzova
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.25024
Abstract: The paper contains a theoretical study of the personal representation of “I-Stranger” interaction. The differentiation of the native-strange and close/ours-alien dichotomies is suggested. The empirical study (N = 100) which highlighted the ambivalent nature of personal representation of “I-Stranger” interaction, its ambiguity and variability has been conducted. The prospects of representation of “I-Stranger” interaction studying in modern multicultural world are stated. The applied aspect of the stated problem can be implemented in the training programs on the personality intercultural sensitivity development.
Abies sibirica Male Reproductive Cones Developmental Shift at Introduction  [PDF]
Elena V. Bazhina
Open Journal of Ecology (OJE) , 2014, DOI: 10.4236/oje.2014.46029

A strong effect of climate on phenological events in conifers has been documented by several studies. To study adaptation of reproductive processes in Abies sibirica Ledeb. to changing environment, the phenology of the development of the species male reproductive cones at introduction was studied. Phenological shift in Abies sibirica meiosis and pollination was observed. An earlier start of male bud reproductive development is founded in V.N. Sukachev Institute of Forest Arboretum resulted in increasing meiosis and pollen irregularities. Insufficient high quality pollen in the species at its pollination stage may be a major factor responsible for the incapability to produce the viable seeds in quantities sufficient for pollination in seed gardens. Responses of the fir male cone development to the current environmental conditions at the Arboretum may be considered as a model of adaptation of the species to climatic changes.

Optimal Time and Opportunity Cost of Job Search in Low-Income Groups: An Out-of-the-Job Search Model  [PDF]
Tamara Todorova, Veselina Dzharova
Modern Economy (ME) , 2010, DOI: 10.4236/me.2010.13022
Abstract: Our paper studies the causes of poverty from the perspective of job search. We show that poor people remain poor because they have less time and initial endowment to search for a better job. Initial endowment is key to successful job search, as one can afford not to work and search longer for a better job. Having an initial endowment, a worker is able to educate or re-qualify himself. Working long hours and obtaining low pay, poor people have little time to look for a better job. Low-paid, low-skilled jobs rarely allow on-the-job search like high-paid positions where with the help of contacts and a lot of idle time professionals seek better jobs. Quitting in order to find a better job increases the opportunity cost of search for poorer people. Since they do not have any accumulated income, they can only live off their salary. With less income and time, poorer people are less likely to get educated since education requires both wealth and free time. But being less educated, they are likely to remain poor as education is a promise for success in contemporary society. Thus, they remain in the vicious circle of poverty. In order to prove this hypothesis we investigate optimal search time for a better job as dependent on factors such as wage rate, individual’s income, education, and skills.
Generalized Option Betas  [PDF]
Sven Husmann, Neda Todorova
Journal of Mathematical Finance (JMF) , 2013, DOI: 10.4236/jmf.2013.33035

This paper extends the option betas presented by Cox and Rubinstein (1985) and Branger and Schlag (2007). In particular, we show how the beta of the underlying asset affects both an option’s covariance beta and its asset pricing beta. In contrast to Branger and Schlag (2007), the generalized option betas coincide if the options are evaluated according to the CAPM option pricing model of Husmann and Todorova (2011). The option betas are presented in terms of Black-Scholes option prices and are therefore easy to use in practice.

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